FU,
1) Metzizah is for medical benefit, therefore no one holds that If metzizah is done in another fashion you do not have to redo the bris.
2) That does not mean that it is not a chelek of the mitzvah.
3) that does not mean that there is not a preferential way to do that part of the mitzvah.
4) Tendler’s stance is irrational and not supportable by anyone, not even the study he co(made up)authored. What he has done is a true chilul hasahem, in any meaning of the word. The biggest proof is the way he has gone about it, including running to the urinal news for his story. Which is akin to publishing something against the yidden in Goebbels ym’s newspaper. I am not sure how he can look himself in the mirror without feeling sick.